Leg unit inserts

ABSTRACT

In an external pressure circulatory assist apparatus of the kind wherein hydraulic pressure is cycled against a patient&#39;&#39;s legs usually in synchronization with the patient&#39;&#39;s heartbeat, means to improve the performance of the apparatus on smaller patients by providing rigid leg inserts adapted to fit between the upper portion of a supine patient&#39;&#39;s legs and a rigid shell for enclosing both the inserts and a hydraulic blanket. The inserts provide means to improve pressure cycle control on a patient&#39;&#39;s legs.

ilnited States'Patent [191 Hagopian et a1.

[451 Jan. 22, 1974 LEG UNIT INSERTS [75] Inventors: Nubar D. Hagopian, Waltham; John M. Colman, Lexington, both of Mass.

[73] Assignee: Medical Innovations, linc., Waltham,

Mass.

22 Filed: Oct. 24, 1972 211 App1.No.: 299,712

[52] US. Cl. 128/24 R, 128/64 [51] Int. Cl A6lh 1/00 [58] Field of Search... 128/24 R, 64, 60, 25 R, 25 B [56] References Cited UNITED STATES PATENTS Dennis 128/24 R MacLeod 128/64 UX 3,403,673 10/1968 3,654,919 4/1972 Birtwell Primary Examiner-Lawrence W. Trapp Attorney, Agent, or FirmRobert A. Cesari et a1.

[5 7 ABSTRACT In an external pressure circulatory assist apparatus of the kind wherein hydraulic pressure is cycled against a patients legs-usually in synchronization with the patients heartbeat, means to improve the performance of the apparatus on smaller patients by providing rigid leg inserts adapted to fit between the upper portion of a supine patients legs and a rigid shell for enclosing both the inserts and a hydraulic blanket. The inserts provide means to improve pressure cycle control on a patients legs.

3 Claims, 4 Drawing Figures LEG UNIT INSERTS BACKGROUND OF THE INVENTION This invention relates to improved external pressure circulatory assist apparatus of the kind wherein hydraulic pressure is cycled against a patients legs, usually in synchronization with the patients heartbeat cycle.

There has been a considerable effort in recent years in developing external pressure assist apparatus to exploit the potential of the process generally discussed in US. Pat. Nos. 3,303,841 to Dennis and 3,654,919 to Birtwell. The more advanced of this work has utilized a liquid-filled blanket wrapped about the legs of a patient and enclosed in a strain-resistant housing that assures pressure is transmitted directly from a pressurecycling source (say, a reciprocating platen positioned between the legs as the patient lies supine) to the liquid-filled blanket wrapped about the leg. Such an arrangement is disclosed in commonly-owned and copending US. application Ser. No. 197,824 filed Nov. 1 l, 1971 by Sauer et al. and is embodied in apparatus commercially available from Medical Innovations, Inc. of Waltham, Mass. under the trademark Cardiassist.

It was noticed, however, that when smaller patients were treated with the above-described apparatus, it was difficult to maintain the desired pressure-time cycle with the apparatus even when adjustments were made in the stroke of the mechanically-actuated platen and in the amount of liquid used in the aforesaid blanket. This problem persisted 'even when the pressure apparatus was constructed to be substantially independent of pumping water in and out of the liquid-filled blanket and dependent primarily on the mechanical pulsation of liquid contained in a substantially non-extensible bladder.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide an improved leg housing for an external pressure circulatory assist apparatus which provides improved pressure coupling between the legs of patients and mechanical pressurizing means.

Other objects of the invention will be obvious to those skilled in the art on reading the instant application.

The above objects have been substantially achieved by constructing a leg unit which reduces the amount of water required in the leg unit during treatment of the patient and also reduces the potential of the occurrence of unsupported bladder area in the leg unit during operation. This apparatus comprises rigid, generally leg-conforming inserts of generally truncated conical shape and positioned between the liquid bladder in direct contact with the inner wall of the rigid housing of the leg unit. These inserts must be formed of substantially non-deformable material; they may not be formed of deformable cushioning materials. Such inserts are advantageously fastened to the restraining housing of the leg unit to prevent movement during use. This coupling can be achieved by use of mechanical fasteners of the conventional type, by providing a high-friction contact surface between the inserts and the housing or by any other means found suitable in a given situation.

Fiberglass-reinforced polyester resin is one material suitable for construction of the leg insert members. Such a material is sufficiently rigid so that it can be used with a hollow or foamor honeycomb-supported core to reduce the overall weight of the inserts and the unit.

Although not wishing to be bound by the theory, the inventors believe that the particular advantage of the invention is primarily the result of avoiding so called end-effects, that is, small effects of pressure in the liquid blanket on the geometry of the blanket at the ends" of the blanket, i.e. near the ankle and at the upper thigh. Although with a non-extensible blanket these effects theoretically would be infinitely small, practical experience shows that a small amount of variation often occurs because of the hurried fit of the blanket when it is placed about the patient or some other such practical consideration. It is the reduction of the annular volume at these end points which is the important aspect of the inserts.

ILLUSTRATIVE EXAMPLE OF THE INVENTION In this application and accompanying drawings there is shown and described a preferred embodiment of the invention and suggested various alternatives and modifications thereof, but it is to be understood that these are not intended to be exhaustive and that other changes and modifications can be made within the scope of the invention. These suggestions are selected and included for purposes of illustration in order that others skilled in the art will more fully understand the invention and the principles thereof and will be able to modify it in "a variety of forms, each as may be best suited in the condition of a particular case.

In the Drawings FIG. 1 is an exploded view of a leg unit useful in external pressure circulatory assist apparatus. The unit is shown with the control and mechanical-actuating mod ules removed.

FIG. 2 is an end view of an insert constructed for use in the invention, said view being taken from the ankle and of the insert.

FIG. 3 is a perspective view of the insert of FIG. 2.

FIG. 4 is a section of the apparatus shown in FlG. 1 showing the relationship of a liquid-containing, pressure-transmitting bladder, the rigid casing and the inserts of the invention.

Referring to FIG. 1, it is seen that a leg unit 10 adapted for use in external pressure circulatory assist treatment comprises an upper housing 12 and a lower housing 14. The upper and lower housings are connected one to the other by slide fasteners consisting of male members 16 mounted on housing 14 and female members 18 on housing 12. Three quick-connecting bolts 19 are utilized to connect the triangular lower housing reinforcing frame 20 to the upper housing reinforcing frame 22. This frame, combined with the hoopstress-resistant configuration of the leg unit provides excellent resistance to pressure-caused distortion of unit 10 by pressure created therein during treatment of a patient. The weight of unit 10 is minimized by providing a gloss-reinforced polyester shell reinforced in the triangular bracing area 24 by a honeycomb construction 26.

Within the housing is a liquid-filled blanket 28 which is adapted to enclose a patients legs. Only a fragment of blanket 28 is shown in FIG. 1. FIG. 4 shows a section of the entire blanket and also shows a mechanical actuator, i.e. a platen 30 mounted for reciprocating contact with blanket 28 and thereby providing a pressure pulse to the blanket and hence to the legs enclosed therein.

Leg inserts 32 are fitted between blanket 28 and upper housing 12 as shown in FIGS. 1 and 4. The curvature of the insert 32 as, for example at 33 should merge smoothly with the inner wall of leg housing unit. The inserts usually have an arc in cross section of from 100 to 180 l or so is the preferred are. They are fastened, as seen in FIG. I, by a snap-type fastener 40 positioned on a strap which is united to the insert at 42.

In one sense, the new leg units can be considered to be solid extensions of the fluid-containing bag itself. In place they function as they would were they permanently attached thereto and, of course, such an integrated structure would be one embodiment of the invention since it would function well in avoiding the socalled end effects, and distributing the hoop stresses as does the combination of a separate inserts and liquid bag. However, the apparatus is more versatile if the inserts are removable.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which might be said to fall therebetween.

What is claimed is: I

1. In external pressure circulatory assist apparatus comprising a rigid housing adapted for holding limbs of a patient and a liquid-filled blanket adapted for transmitting pressure to said limbs from a mechanical pressure-causing device, the improvement comprising a pair of rigid non-compressible inserts of generally truncated semi-conical shape adapted to be placed over each of said patient's limbs, said inserts between said blanket and said rigid housing, said inserts forming means adapted to substantially decrease the annular distance between the patients limbs and the inner walls of said housing.

2. Apparatus as defined in claim 1 wherein said inserts are mechanically fastened to said housing.

3. Apparatus as defined in claim 1 wherein said inserts form, with the interior walls of said leg housing, a continuous curved wall in contact with said liquidfilled blanket. 

1. In external pressure circulatory assist apparatus comprising a rigid housing adapted for holding limbs of a patient and a liquid-filled blanket adapted for transmitting pressure to said limbs from a mechanical pressure-causing device, the improvement comprising a pair of rigid non-compressible inserts of generally truncated semi-conical shape adapted to be placed over each of said patient''s limbs, said inserts between said blanket and said rigid housing, said inserts forming means adapted to substantially decrease the annular distance between the patient''s limbs and the inner walls of said housing.
 2. Apparatus as defined in claim 1 wherein said inserts are mechanically fastened to said housing.
 3. Apparatus as defined in claim 1 wherein said inserts form, with the interior walls of said leg housing, a continuous curved wall in contact with said liquid-filled blanket. 